Broadband telescope

ABSTRACT

The light of a broad energy band can be observed by reflecting the light of the broad energy band, for example, the light from the visible light region to the x-ray region at a high reflectance respectively, by a composite telescope including a normal incidence optical system and an oblique incidence optical system. A broadband telescope comprise an oblique incidence optical system unit in which the light is obliquely incident on a surface part for reflecting the incident light, a normal incidence optical system unit in which the light is substantially vertically incident on a surface part for reflecting the incident light, and an analyzer for spectrum analysis of the light reflected by the surface part of the obliquely incidence optical system unit and the light reflected by the surface part of the normal incidence optical system unit.

TECHNICAL FIELD

The present invention relates to a broadband telescope, moreparticularly to a broadband telescope suitable for using for astronomicobservation where light of a broad energy band is made incident.

BACKGROUND ART

Conventionally, there is known a normal incidence telescope forobserving light of a predetermined energy, which comprises a reflectingmirror, on the surface of which a multilayer film is formed and whichreflects only light of a predetermined energy corresponding to themultilayer film at high reflectance, and a detector such as asemiconductor detector to which reflected light reflected by thereflecting mirror is condensed and which detects the light of apredetermined energy.

On the other hand, in the astronomic observation, since an apparentenergy level considerably fluctuates due to collective motion and redshift, light is not observed in an energy band anticipated in restsystem. A multilayer film of a conventional reflecting mirror has anarrow band in which only light of a predetermined energy is reflectedat high reflectance, so that discovery of line spectrum in a celestialbody, which fluctuates remarkably, is not expected.

Specifically, in the above-described astronomic observation, a telescopecapable of observing the light in a broad energy band is desired.Particularly, since a complex index of refraction is approximately 1,and δ(=1-n) and extinction coefficient K is sufficiently smaller than 1in a region extending from extreme ultraviolet ray to x-ray, areflectance of normal incidence does not reach 1% in bulk. Besides,because light in a region extending from extreme ultraviolet ray tox-ray is absorbed by atmospheric air, a telescope capable of performingobservation outside aerosphere is desired.

However, in the conventional normal incidence telescope, the multilayerfilm formed on the surface of the reflecting mirror exhibits highreflectance only to light of a predetermined energy, only the light of apredetermined energy reflected at high reflectance by the reflectingmirror can be observed, on which the multilayer film was formed, andthere has been a problem that observation could not been performed withrespect to light in a broad energy band which is the light in a regionextending from visible light to x-ray, for example.

Further, in the conventional normal incidence telescope, singletelescope can only observe the light of a predetermined energycorresponding to the multilayer film of the reflecting mirror, it isrequired to use a plurality of normal incidence telescopes each havingthe reflecting mirror on which the multilayer film reflecting light ofdifferent energy is formed in order to observe the light in a broadenergy band by the conventional normal telescope. As a result, a newproblem such as cost increase and securing of a wide space for arranginga plurality of normal incidence telescopes occurs.

Furthermore, when a plurality of the conventional normal incidencetelescopes are used so as to have the reflecting mirrors on which themultilayer films reflecting light of different energy are formed, it isrequired to control a plurality of the normal incidence telescopes,there existed a problem of reduction of efficiency.

On the other hand, an oblique incidence optical system is known forobtaining high reflectance with respect to the region extending fromvisible light to x-ray, but the oblique incidence optical system has hadvarious problems such as a narrow field of vision and a small effectivearea.

The present invention has been made in view of the above-describedproblems involved in prior art, and its object is to provide a broadbandtelescope that utilizes the advantages of the normal incidence opticalsystem and the oblique incidence optical system well to make it possibleto observe light in a broad energy band.

Further, another object of the present invention is to provide abroadband telescope in which a composite telescope of the normalincidence optical system and the oblique incidence optical systemreflects each light rays in a broad energy band extending from visiblelight to x-ray, for example, at high reflectance to achieve costreduction and space saving and to make it possible to efficientlyobserve the light in a broad energy band.

DISCLOSURE OF INVENTION

To achieve the above-described objects, the present invention comprises:an oblique incidence optical system unit where light is made incidentobliquely to a surface part that reflects incident light; a normalincidence optical system unit where light is made incident substantiallyvertically to a surface part that reflects incident light; and adetector to which reflected light reflected by the surface part of theoblique incidence optical system unit and reflected light reflected bythe surface part of the normal incidence optical system unit are madeincident and which spectrally detects the incident light.

Therefore, according to the present invention, when the light in a broadenergy band are made incident to the surface part of the obliqueincidence optical system unit and the surface part of the normalincidence optical system unit, each light in the broad energy band thatis the broad energy band extending from visible light to x-ray, forexample, is reflected at high reflectance by the surface part of theoblique incidence optical system unit and the surface part of the normalincidence optical system unit, and the detector spectrally detects thelight reflected by the surface part of the oblique incidence opticalsystem unit and the surface part of the normal incidence optical systemunit. Thus, the advantages of the normal incidence optical system andthe oblique incidence optical system are utilized well and the light inthe broad energy band can be severally observed.

Then, since a confocal composite telescope of the normal incidenceoptical system and the oblique incidence optical system reflects eachlight in a broad energy band at high reflectance, cost reduction andspace saving can be achieved and the light in a broad energy band can beefficiently observed simultaneously.

Further, in the present invention, the normal incidence optical systemunit may be located inside comparing to the oblique incidence opticalsystem unit, and the detector may be located on an optical axis. Thisrealizes further space saving and the entire telescope can be smaller.

Furthermore, the present invention comprises: an oblique incidenceoptical system unit, which has a first reflecting mirror reflectingincident light at a first surface part made up of paraboloid ofrevolution, and a second reflecting mirror reflecting light, which isreflected at the surface part of the first mirror, at a second surfacepart made up of hyperboloid of revolution; a normal incidence opticalsystem unit, which has a third reflecting mirror that has a thirdsurface part on which a multilayer film is formed, which continuouslychanges a periodic length along its depth direction to reflect eachlight of a predetermined energy in a region extending from vacuumultraviolet ray to extreme ultraviolet ray and has high reflectance dueto total reflection over a visible light region, and reflects theincident light at the third surface part, and a fourth reflecting mirrorthat has a fourth surface part on which a multilayer film is formed,which continuously changes the periodic length along its depth directioncorresponding to the third surface part of the third reflecting mirrorto reflect each light of a predetermined energy in the region extendingfrom vacuum ultraviolet ray to extreme ultraviolet ray and has highreflectance due to total reflection over the visible light region, andreflects the light, which is reflected at the third surface part of thethird reflecting mirror, at the fourth surface part; and a detector towhich reflected light reflected at the second surface part of the secondreflecting mirror and reflected light reflected at the fourth reflectingmirror are made incident and which spectrally detects the incidentlight.

Thus, according to the present invention, when light in a broad energyband are made incident to the first surface part of the first reflectingmirror of the oblique incidence optical system unit and the thirdsurface part of the third reflecting mirror of the normal incidenceoptical system unit, the oblique incidence optical system unit reflectseach light in a region extending from visible light to hard x-ray out ofthe light in a broad energy band at high reflectance, the normalincidence optical system unit reflects each light in a region extendingfrom visible light to extreme ultraviolet ray out of the light in abroad energy band at high reflectance, and the detector spectrallydetects the light reflected at the surface part of the oblique incidenceoptical system unit and the surface part of the normal incidence opticalsystem unit, so that the light in a broad energy band, particularly thelight in the region extending from visible light to x-ray can beobserved.

Then, since the confocal composite telescope of the normal incidenceoptical system and the oblique incidence optical system reflects eachlight in a broad energy band at high reflectance, cost reduction andspace saving can be achieved and the light in a broad energy band can beefficiently observed simultaneously.

Further, in the present invention, the first reflecting mirror and thesecond reflecting mirror of the oblique incidence optical system unitconstitute an aspherical reflecting mirror of an approximate cylindricalshape, the normal incidence optical system unit is located within theinner diameter side of the aspherical reflecting mirror, and thedetector is located on the optical axis. This realizes further spacesaving and the entire telescope can be smaller.

Furthermore, in the present invention, the detector may be asuperconducting tunnel junction device.

Accordingly, with the superconducting tunnel junction device thatfunctions as a detector having high sensitivity and spectroscopiccapability in a broadband extending from infrared ray to x-ray, eachlight in a broad energy band reflected by a single or a plurality ofreflecting mirror(s) can be spectrally detected by a single detector.

Moreover, in the present invention, the telescope may comprise a filterthat makes only light, which has higher energy than the reflected lightreflected at the surface part of the normal incidence optical systemunit out of the reflected light reflected at the surface part of theoblique incidence optical system unit, incident selectively to thedetector.

Consequently, since only light having a predetermined energy out of thereflected light reflected at the surface part of the oblique incidenceoptical system unit is made incident selectively to the detectorcorresponding to the reflected light reflected at the surface part ofthe normal incidence optical system unit, it becomes possible to changea range of energy of the reflected light made incident from each of theoblique incidence optical system unit and the normal incidence opticalsystem unit to the detector by the filter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view of a conceptual constitution illustratingan example of an embodiment of a broadband telescope according to thepresent invention.

FIG. 2 is an explanatory view of a schematic constitution illustratingan example of an embodiment of a broadband telescope according to thepresent invention.

FIG. 3 is a perspective explanatory view illustrating mainly an obliqueincidence optical system unit of the broadband telescope according tothe present invention.

FIG. 4 is a perspective explanatory view illustrating mainly a normalincidence optical system unit of the broadband telescope according tothe present invention.

FIG. 5(a) is an explanatory view illustrating mainly the surface part ofa reflecting mirror as a primary mirror of the normal incidence opticalsystem unit of the broadband telescope according to the presentinvention, and FIG. 5(b) is a partially enlarged explanatory view of A-Asectional view in FIG. 5(a).

FIG. 6(a) is a graph illustrating the reflectance of the surface of asuperconducting tunnel junction device, and FIG. 6(b) is a graphindicating the transmittance of the superconducting tunnel junctiondevice.

FIG. 7 is a graph illustrating an example of energy resolution in aregion extending from extreme ultraviolet ray to x-ray of thesuperconducting tunnel junction device.

FIG. 8 is a graph illustrating an example of energy resolution in anx-ray region of the superconducting tunnel junction device.

FIGS. 9(a), (b), (c) and (d) are graphs illustrating examples of energyresolution in a soft x-ray region of the superconducting tunnel junctiondevice, and FIGS. 9(e), (f), (g) a (h) are graphs illustrating examplesof energy resolution in an extreme ultraviolet ray region of thesuperconducting tunnel junction device.

FIG. 10 is a graph illustrating synthesized reflectance characteristicsof the oblique incidence optical system unit and the normal incidenceoptical system unit in one example of the embodiment of the broadbandtelescope according to the present invention.

FIG. 11 is a graph illustrating synthesized reflectance characteristicsof the oblique incidence optical system unit and the normal incidenceoptical system unit in another example of the embodiment of thebroadband telescope according to the present invention.

FIG. 12 is an explanatory view illustrating a first Lagrangian point(L1) as an example for positioning the broadband telescope according tothe present invention.

FIG. 13 is an explanatory view illustrating an example of specificdimensional settings of the broadband telescope according to the presentinvention.

FIGS. 14(a) and (b) are graphs illustrating the transmittance of an Al/C(aluminum/carbon) metal thin film filter.

Explanation of Reference Numerals

-   10 Broadband telescope-   12 Oblique incidence optical system unit-   12 a Paraboloid-   12 b Hyperboloid-   12 c Aspherical reflecting mirror-   14 Normal incidence optical system unit-   16 Superconducting tunnel junction device-   20 Main unit-   20 a Inside-   20 b Bottom part-   20 c Opening-   20 d Front section-   20 e Rear section-   20 f Wall-   20 g Support-   20 h Front arm-   20 i Rear arm-   30, 32 Reflecting mirror-   30 a, 32 a Surface part-   30 b, 30 c, 32 b, 32 c End part-   34, 44, 50 Filter-   34 a Hole-   40, 42 Reflecting mirror-   40 a Main unit-   40 b, 42 a Surface part-   40 c Rear surface part-   40 d Hole part-   40 e Multilayer film-   40 e-1 First layer-   40 e-2 Second layer-   40 ee Surface

BEST MODE FOR IMPLEMENTING THE INVENTION

Hereinafter, the embodiments of the broadband telescope according to thepresent invention will be described in detail with reference to theaccompanying drawings.

FIG. 1 shows the explanatory view of a conceptual constitutionillustrating an example of the embodiments of the broadband telescopeaccording to the present invention, and FIG. 2 shows the explanatoryview of a schematic constitution illustrating an example of theembodiments of the broadband telescope according to the presentinvention.

The broadband telescope 10 according to the present invention isconstituted to comprise an oblique incidence optical system unit 12where light is made incident to reflecting mirrors 30 obliquely, anormal incidence optical system unit 14 where light is made incident toa reflecting mirror 40 approximately vertically, and a superconductingtunnel junction device (STJ) 16 as a detector into which the reflectedlight from the oblique incidence optical system unit 12 and thereflected light from the normal incidence optical system unit 14 arecondensed.

It is to be noted that, as shown in FIG. 2, the broadband telescope 10according to the present invention comprises a cylindrical main unit 20whose inside 20 a is hollow. One end part of the main unit 20 is closedby an approximately circular bottom part 20 b, and the other end part isopen by an approximately circular opening 20 c. Further, the telescopehas a wall 20 f, which divides the main unit 20 into a front section 20d and a rear section 20 e, and a support 20 g extended from the wall 20f.

Further, the central axis of the main unit 20 coincides with an axispassing through the center of the optical system of the obliqueincidence optical system unit 12 that is an axis passing through thecenter of the optical system of the normal incidence optical system unit12, that is, an axis o-o (refer to dashed line in FIG. 2) of thebroadband telescope 10.

Herein, the oblique incidence optical system unit 12 is constituted tocomprise approximately cylindrical aspherical reflecting mirrors 12 c ofso-called Wolter type I and a filter 34 disposed on the wall 20 f of themain unit 20 (refer to FIG. 3).

The aspherical reflecting mirror 12 c is constituted by a paraboloid 12a, which consists of a plurality of reflecting mirrors 30 disposed nearthe opening 20 c of the front section 20 d of the main unit, and ahyperboloid 12 b that consists of a plurality of reflecting mirrors 32near the wall 20 f of the main unit 20.

The entire body of each of a plurality of the reflecting mirrors 30,which constitute the paraboloid 12 a, is in an approximately cylindricalbody and includes a surface part 30 a formed as the paraboloid ofrevolution. On the other hand, the entire body of each of a plurality ofthe reflecting mirrors 32, which constitute the hyperboloid 12 b, is inan approximately cylindrical body and includes a surface part 32 aformed as the hyperboloid of revolution. Then, Au (gold) or Pt(platinum) is coated on the surface part 30 a of the reflecting mirrors30 and the surface part 32 a of the reflecting mirrors 32.

Then, the reflecting mirrors are disposed concentrically around theoptical axis o-o in a multiple state such that each of a plurality ofthe reflecting mirrors 30 and each of a plurality of the reflectingmirrors 32 corresponds one to one, and the paraboloid 12 a and thehyperboloid 12 b are arranged in this order from the opening 20 c of themain unit 20. Specifically, one end part 30 b of the reflecting mirrors30 with the paraboloid 12 is located near the opening 20 c of the mainunit 20, the other end part 30 c of the reflecting mirrors 30 and oneend part 32 b of the reflecting mirrors 32 are adjacent to each other,and another end part 32 c of the reflecting mirrors 32 is located closerto the wall 20 f of the main unit 20.

The filter 34 is in an approximate ring shape where an approximatecircular hole 34 a is formed at the central area, which is disposed inthe wall 2of of the main unit 20 and located near the end part 32 c ofthe reflecting mirrors 32. The filter 34 blocks light having energy sameas that of extreme ultraviolet ray or less.

On the other hand, the normal incidence optical system unit 14 islocated within the inner diameter side of the approximately cylindricalaspherical reflecting mirrors 12 c, which consist of the paraboloid 12 aand the hyperboloid 12 b of the oblique incidence optical system unit12, and is constituted to comprise a reflecting mirror 40 supported bythe support 20 g in the front section 20 d of the main unit 20, areflecting mirror 42 supported by the front arm 20 h extended from thesupport 20 g, and a filter 44 supported by rear arm 20 i extended fromthe support 20 g (refer to FIG. 4).

The normal incidence optical system unit 14, which consists of thereflecting mirror 40, the reflecting mirror 42 and the filter 44,constitutes a so-called Cassegrain-type telescope within the innerdiameter side of the aspherical reflecting mirror 12 c of the obliqueincidence optical system unit 12.

In other words, the surface part 40 b of the reflecting mirror as theprimary mirror and the surface part 42 a of the reflecting mirror 42 asa secondary mirror face each other, the reflecting mirror 42 as thesecondary mirror turns back an optical path, and focuses it on the rearsurface part 40 c of the reflecting mirror 40 as the primary mirror. Itis to be noted that the superconducting tunnel junction device 16 isarranged on the focused position in this embodiment. Further, thereflecting mirror 40, the reflecting mirror 42 and the filter 44 aredisposed such that the center of the reflecting mirror 40, the center ofthe reflecting mirror 42 and the center of the filter 44 coincide withthe optical axis o-o of the broadband telescope 10.

The entire reflecting mirror 40 is in a circular dish-shaped body 40 a,and a hole part 40 d that opens on the surface part 40 b and the rearsurface part 40 c is formed on the central area. Further, the surfacepart 40 b of the dish-shaped body 40 a is formed as the paraboloid ofrevolution, which is concavely recessed centering around the hole part40 d (refer to FIG. 4 and FIGS. 5(a), (b)).

Then, in the entire region of the surface part 40 b of the approximatelyring shape, a first layer 40 e-1 having a predetermined refractive indexis formed and a second layer 40 e-2, which has a refractive indexdifferent from the refractive index of the first layer 40 e-1, islaminated on the first layer 40 e-1. Furthermore, the first layer 40 e-1and the second layer 40 e-2 laminated on the first layer 40 e-1 make oneset, a predetermined number n (‘n’ is a positive integer) of laminationsare laminated to form a multilayer film 40 e on the surface part 40 b.

Specifically, the first layer 40 e-1 is made from heavy element such asNi (nickel) and Mo (molybdenum), for example, while the second layer 40e-2 is made from light element such as C (carbon) and Si (silicon), forexample.

Thus, when thin films having different refractive indexes are superposedin a multilayered state and a periodic length d, which corresponds tothe film thickness of a set of the first layer 40 e-1 and the secondlayer 40 e-2, is formed so as to utilize Bragg reflection, light madeincident to the multilayer film is reflected at the boundary surfacebetween the first layer 40 e-1 and the second layer 40 e-2 to causeinterference of the light reflected at the boundary surface between thefirst layer 40 e-1 and the second layer 40 e-2, and light having apredetermined energy is reflected at high reflectance.

Herein, the multilayer film 40 e formed on the surface part 40 b of thereflecting mirror 40 is a multilayer film having different periodiclengths d. In short, the periodic lengths d of the multilayer film 40 eare continuously changed in the depth direction (refer to FIG. 5(b)).More specifically, in the multilayer film 40 e formed on the surfacepart 40 b of the reflecting mirror 40, the periodic length d is designedto be shorter as a set of layers backs away from a surface 40 ee and theperiodic length d is designed to be longer as it approaches the surface40 ee along the depth direction of the multilayer film 40 e.

Therefore, as shown in FIG. 5(b), a periodic length d₁ farthermost awayfrom the surface 40 ee, a periodic length d₂ at the halfpoint in thedepth direction, and a periodic length d₁ in the vicinity of the surface40 ee of the multilayer film 40 e are in the relationship of theperiodic length d₁<the periodic length d₂<the periodic length d₃.

The periodic lengths d of the multilayer film 40 e formed on the surfacepart 40 b of the reflecting mirror 40 are designed to be continuouslychanged in the depth direction of the multilayer film 40 e so as tocorrespond to each light having a predetermined energy in the rangeextending from vacuum ultraviolet ray to extreme ultraviolet ray.Accordingly, energy of light reflected on the boundary surface betweenthe first layer 40 e-1 and the second layer 40 e-2 utilizing Braggreflection is different on different periodic lengths d (periodic lengthd₁, d₂, d₃, for example) in the multilayer film 40 e of the reflectingmirror 40.

It is to be noted that, in this specification, the “multilayer filmwhere the periodic lengths d are continuously changed in the depthdirection” is optionally referred to as a “supermirror”.

On the other hand, the surface portion 42 a of the reflecting mirror 42has a convex surface and is constituted by the supermirror. Thesupermirror of the reflecting mirror 42 is designed corresponding tovarious conditions such as the type and the focal length of thesupermirror that constitutes the surface part 40 b as the concavesurface of the reflecting mirror 40. Then, the surface part 42 a of thereflecting mirror 42 reflects light reflected at the surface part 40 bof the reflecting mirror 40 at high reflectance.

It is to be noted that known technology can be used to form thesupermirror on the surface part 40 b of the reflecting mirror 40 and thesurface part 42 a of the reflecting mirror 42, and the detaileddescription of a deposition apparatus and a deposition method will beomitted.

Further, the filter 44 is in an approximate disc-shaped body, which issupported by the rear support 20 i of the main unit 20 and located inthe vicinity of the hole part 40 d of a rear surface part 40 c side ofthe reflecting mirror 40. The filter 44 adjusts the quantity of light.

Next, the superconducting tunnel junction device 16 is a type of aJosephson device, which has a structure that a thin insulation film(aluminum oxide, for example) is sandwiched by superconducting metalthin films (niobium, aluminum, titanium, for example).

The superconducting tunnel junction device 16 is a detector to which thereflected light from the oblique incidence optical system unit 12 andthe reflected light from the normal incidence optical system unit 14 arecondensed, as described above. More specifically, it operates atcryogenic temperature of approximately 0.3K, and when light is madeincident to the superconducting tunnel junction device 16, energy of theincident light is absorbed by the superconducting metal thin films.

Subsequently, when the energy of the incident light is absorbed by thesuperconducting thin films of the superconducting tunnel junction device16, dissociation of Cooper pair and generation of phonons in thesuperconducting metal thin films are caused. Moreover, process where thegenerated phonons dissociate Cooper pair is caused within the time ofapproximately 10⁻¹² second.

At this point, quasiparticles are produced and the quasiparticles passthrough the insulation film by quantum tunneling effect, so thatelectric current in proportion to the energy of incident light isgenerated and taken out as a signal by using a predetermined circuitsystem, and the device operates as the detector.

As described, the superconducting tunnel junction device 16 functions asa detector having high sensitivity and spectroscopic capability in abroadband extending form infrared ray to x-ray.

Specifically, FIG. 6(a) shows the reflectance on the surface of thesuperconducting tunnel junction device 16, and FIG. 6(b) shows thetransmittance of the superconducting tunnel junction device 16. As it isclear from the reflectance and transmittance of the superconductingtunnel junction device 16, photon absorptance of the superconductingtunnel junction device 16 is 95% or higher.

Moreover, the superconducting tunnel junction device 16 has very highphoton absorptance in the region extending from extreme ultraviolet tosoft x-ray, so that when the superconducting tunnel junction device 16having behavior of producing signals by photon absorption as describedabove, spectral detection of light is realized in a region extendingfrom visible light to hard x-ray.

Meanwhile, FIG. 7 shows the graph illustrating an example of energyresolution in a region extending from extreme ultraviolet ray to x-rayof the superconducting tunnel junction device 16, FIG. 8 shows the graphillustrating an example of energy resolution in an x-ray region of thesuperconducting tunnel junction device 16, FIGS. 9(a), (b), (c) and (d)shows the graphs illustrating examples of energy resolution in a softx-ray region of the superconducting tunnel junction device 16, and FIGS.9(e), (f), (g) and (h) shows the graphs illustrating examples of energyresolution in an extreme ultraviolet ray region of the superconductingtunnel junction device 16.

Then, a filter 50 is disposed in the prestage of the superconductingtunnel junction device 16. The filter 50 is in an approximatedisc-shaped body and blocks infrared ray. For this reason, the filter 50blocks infrared ray and infrared ray is not made incident to thesuperconducting tunnel junction device 16. Therefore, temperature riseof the superconducting tunnel junction device 16 is prevented, goodoperation environment is maintained, and more accurate detection resultcan be obtained.

Further, when light is made incident to the superconducting tunneljunction device 16, the electric current in proportion to the energy ofthe incident light is generated. Two circuit systems corresponding tosignal levels are provided as the circuit system that takes out signalsbased on the electric current generated in this manner. Specifically, acircuit primarily for high energy such as x-ray and a circuit primarilyfor low energy such as visible light are disposed.

In the above-described constitution, when the broadband telescope 10according to the present invention is used in astronomic observation,light in a broad energy band is made incident obliquely to the surfacepart 30 a of the reflecting mirror 30 of the oblique incidence opticalsystem unit 12 and is made incident approximately perpendicularly to thesurface part 40 b of the reflecting mirror 40 of the normal incidenceoptical system unit 14.

Then, in the oblique incidence optical system unit 12, light having thesame energy as that of hard x-ray or less out of light in a broad energyband, which has been made incident obliquely to the surface part 30 a ofthe reflecting mirror 30, is reflected twice by the asphericalreflecting mirror 12 c of the oblique incidence optical system unit 12.

In other words, when light in a broad energy band is made incident tothe end part 30 b of each of a plurality of the reflecting mirrors 30,which constitute the paraboloid 12 a of the oblique incidence opticalsystem unit 12, light having the same energy as that of hard x-ray orless out of light in a broad energy band, which has been made incidentobliquely to the surface part 30 a of the reflecting mirror 30, isreflected at the surface part 30 a of the reflecting mirror 30. Then,the light reflected at the surface part 30 a of the reflecting mirror 30is made incident to the surface part 32 a of each of a plurality of thereflecting mirrors 32 that constitute the hyperboloid 12 b of theoblique incidence optical system unit 12, and reflected at the surfacepart 32 a of the reflecting mirror 32.

The light reflected at the surface part 32 a of the reflecting mirror32, that is, light in the region extending from visible light to hardx-ray out of light in a broad energy band that has been made incident tothe surface part 30 a of the reflecting mirror 30 is made incident tothe filter 34. Then, the filter 34 blocks light having the same energyas that of extreme ultraviolet ray or less, light in the regionextending from soft x-ray to hard x-ray transmits the filter 34, andcondensed into the superconducting tunnel junction device 16 (refer toFIG. 10).

On the other hand, in the oblique incidence optical system unit 14, eachlight having a predetermined energy out of light in a broad energy band,which has been made incident to the surface part 40 b of the reflectingmirror 40 as the primary mirror, transmits the multilayer film 40 e onthe surface part 40 b of the reflecting mirror 40 in the depth directionaccording to an energy size, and is reflected at the boundary surfacebetween the first layer 40 e-1 and the second layer 40 e-2, which has acorresponding periodic length d.

Then, interference of the reflected light reflected at the boundarysurface between the first layer 40 e-1 and the second layer 40 e-2 isgenerated, and as a result, each light in the region extending fromvacuum ultraviolet ray to extreme ultraviolet ray out of the incidentlight in a broad energy band is reflected at high reflectance.

On the other hand, light in the region of visible light having a lowerenergy than that of the region extending from vacuum ultraviolet ray toextreme ultraviolet ray is severally reflected at the surface 40 ee ofthe multilayer film 40 e on the surface part 40 b of the reflectingmirror 40 at high reflectance by total reflection (specular reflection).

As a result, the reflectance of the surface part 40 b of the reflectingmirror 40 is reflectance where the reflectance of each boundary surfacebetween the first layer 40 e-1 and the second layer 40 e-2, which has apredetermined periodic length d, of the multilayer film 40 e and thereflectance of the surface part 40 e e of the multilayer film 40 e aresuperposed (refer to FIG. 10). Accordingly, the surface part 40 b of thereflecting mirror 40 reflects each light in the region extending fromvisible light to extreme ultraviolet ray out of the incident light in abroad energy band at high reflectance.

The light reflected by the supermirror that constitutes the surface part40 b of the reflecting mirror 40 is reflected by the supermirror thatconstitutes the surface part 42 a of the reflecting mirror 42 as thesecondary mirror.

Herein, the supermirror that constitutes the surface part 42 a of thereflecting mirror 42 is designed corresponding to the supermirror thatconstitutes the surface part 40 b of the reflecting mirror 40 in orderto reflect the light reflected at the surface part 40 b of thereflecting mirror 40 at high reflectance. Therefore, each light in theregion extending from visible light to extreme ultraviolet ray, whichhas been reflected by the surface part 40 b of the reflecting mirror 40at high reflectance, out of the light in a broad energy band, which hasbeen made incident to the surface part 40 b of the reflecting mirror 40at high reflectance, is reflected at the surface part 42 a of thereflecting mirror 42 at high reflectance.

Subsequently, the light reflected at the surface part 42 a of thereflecting mirror 42, that is, each light in the region extending fromvisible light to extreme ultraviolet ray out of the light in a broadenergy band, which has been made incident to the surface part 40 b ofthe reflecting mirror 40, goes through the hole part 40 d of thereflecting mirror 40, transmits the filter 44, and is condensed into thesuperconducting tunnel junction device 16.

When the light in the region extending form soft x-ray to hard x-ray,which is the reflected light from the oblique incidence optical systemunit 12, and the light in the region extending form visible light toextreme ultraviolet ray, which is the reflected light from the normalincidence optical system unit 14, out of the light in a broad energyband that has been made incident to the broadband telescope 10 arecondensed and made incident into the superconducting tunnel junctiondevice 16, the electric current in proportion to the energy of lightthat has been made incident as described above is generated.

At this point, when the electric current is generated based on the lightin the region extending form soft x-ray to hard x-ray, which is thereflected light from the oblique incidence optical system unit 12, thesignal is taken out in the circuit for high energy, and when theelectric current is generated based on the light in the region extendingform visible light to extreme ultraviolet ray, which is the reflectedlight from the normal incidence optical system unit 14, the signal istaken out in the circuit for low energy, and light in the regionextending from visible light to hard x-ray is spectrally detected.

As described above, since the broadband telescope 10 according to thepresent invention comprises: the oblique incidence optical system unit12 having the aspherical reflecting mirror 12 c; the oblique incidenceoptical system unit 14 having the reflecting mirror 40 on which thesupermirror corresponding to light in the region extending from visiblelight to extreme ultraviolet ray is formed; and the superconductingtunnel junction device 16 having high sensitivity and spectroscopiccapability in a broadband extending from infrared ray to x-ray, theadvantages of the normal incidence optical system and the obliqueincidence optical system are utilized well. Thus, a single telescopethat is the confocal composite telescope of the normal incidence opticalsystem and the oblique incidence optical system reflects light in abroad energy band of the range extending from visible light to hardx-ray at high reflectance, and the superconducting tunnel junctiondevice 16 spectrally detects the light.

For this reason, the light in a broad energy band, particularly thelight in the range extending from visible light to x-ray can be observedby the broadband telescope 10 according to the present invention.

Furthermore, in the broadband telescope 10 according to the presentinvention, the single telescope that is the confocal composite telescopeof the normal incidence optical system and the oblique incidence opticalsystem reflects light in a broad energy band of the range extending fromvisible light to hard x-ray at high reflectance, which eliminates theneed of using a plurality of telescopes. Thus, cost reduction and spacesaving can be achieved and the light in a broad energy band can beefficiently observed simultaneously.

Furthermore, in the broadband telescope 10 according to the presentinvention, the single telescope reflects light in a broad energy band ofthe range extending from visible light to hard x-ray at highreflectance, so that only one superconducting tunnel junction device 16may be disposed to which the reflected light from the oblique incidenceoptical system unit 12 and the reflected light from the normal incidenceoptical system unit 14 are condensed, by which cost can be reduced and asingle cooler for cooling the superconducting tunnel junction device 16is sufficient. Thus, further space saving can be realized in anastronomical satellite in which the broadband telescope 10 is mounted inperforming astronomic observation.

It is to be noted that the superconducting tunnel junction device 16 isdisposed at the rear surface side of the opening (that is, the end part30 b side of the reflecting mirror 30) of the aspherical reflectingmirror 12 c of the oblique incidence optical system unit 12 and the rearsurface side of the reflecting mirror 40 as the primary mirror of thenormal incidence optical system unit 14, which facilitates the mountingof a cooling system such as the cooler for cooling the superconductingtunnel junction device 16.

Further, the broadband telescope 10 according to the present inventioncan be constituted so as to dispose the normal incidence optical systemunit in an approximate columnar-shaped dead space formed in an innerdiameter side of the aspherical reflecting mirror in the obliqueincidence telescope so-called Wolter type I. For this reason, sizereduction of the entire broadband telescope is easy, and the designknow-how, etc. of the oblique incidence telescope can be utilized insuch occasion.

Then, in the oblique incidence optical system unit 14, aberrationcorrection can be performed by two mirrors, which are the reflectingmirror 40 as the primary mirror and the reflecting mirror 42 as thesecondary mirror. Further, since the superconducting tunnel junctiondevice 16 is the detector that can perform one photon spectral detectionfrom infrared ray to x-ray, it can separately identify the photon evenif the observation scope of the oblique incidence optical system unit 12and the normal incidence optical system unit 14 is different from eachother.

It is to be noted that the above-described embodiments can be modifiedinto (1) to (7) described below.

(1) In the above-described embodiments, the filter 34 of the obliqueincidence optical system unit 12 blocks light having the same energy asthat of extreme ultraviolet ray or less, and the periodic length d ofthe multilayer film 40 e on the surface part 40 b of the reflectingmirror 40 corresponds to each light having a predetermined energy in theregion extending from vacuum ultraviolet ray to extreme ultraviolet ray,but it goes without saying that the invention is not limited to this.

For example, the filter 34 may be modified to block light having thesame energy as that of soft x-ray or less, and the periodic length d ofthe multilayer film 40 e on the surface part 40 b of the reflectingmirror 40 may be modified to correspond to each light having apredetermined energy in the region extending from vacuum ultraviolet rayto soft x-ray. As a result, since light having the same energy as thatof hard x-ray or less, the synchronized reflectance of the obliqueincidence optical system unit 12 and the normal incidence optical systemunit 14 is as shown in FIG. 11 unlike FIG. 10.

As described, when the filter 34 is modified so as to selectivelytransmit only light having higher energy than that of the reflectedlight from the normal incidence optical system unit 14, the range ofenergy distributed to the oblique incidence optical system unit and thenormal incidence optical system unit respectively can be changed by thefilter (refer to FIG. 10 and FIG. 11).

Furthermore, although the filter 44 adjusts the quantity of light in theabove-described embodiments, it goes without saying that the inventionis not limited to this. The filter 44 may be used for adjusting thequantity of light or band selection to the reflected light from thenormal incidence optical system unit 14. Alternatively, the filter 44may not be disposed to simplify the constitution of the normal incidenceoptical system unit 14.

(2) In the above-described embodiments, deposition of Au (gold) or Pt(platinum) is performed on the surface part 30 a of the reflectingmirror 30 and the surface part 32 a of the reflecting mirror 32 of theoblique incidence optical system unit 12, but it goes without sayingthat the invention is not limited to this. A multilayer film or asupermirror may be formed on the surface part 30 a of the reflectingmirror 30 and the surface part 32 a of the reflecting mirror 32. Thismakes it possible to maintain high reflectance up to hard x-ray.

(3) In the above-described embodiments, top coating of Pt or the likemay be applied to the uppermost layer of the reflecting mirror 40 andthe reflecting mirror 42, which are constituted by the supermirror ofthe normal incidence optical system 12, which is the surface 40 ee asthe uppermost layer of the multilayer film 40 e on the surface part 40 bas shown in FIG. 5(b) in the case of the reflecting mirror 40, forexample. This can further improve the reflectance with respect to lightin the region of visible light having lower energy than that of theregion extending from vacuum ultraviolet ray to extreme ultraviolet ray.

Further, the change of the periodic lengths d of the supermirror is notlimited to the above-described embodiments. In the case where aparticular wavelength does not make sense in observation, the particularwavelength may be eliminated and the periodic lengths d may be changedto correspond to necessary wavelengths.

Moreover, in the above-described embodiments, the same supermirror isformed on the entire region of the surface part 40 b of the reflectingmirror 40 of the normal incidence optical system 12, that is, so as toform one type of supermirror on the reflecting mirror 40, but it goeswithout saying the invention is not limited to this. The surface part 40b of the reflecting mirror 40 may be divided into a plurality of regionsand supermirrors of different types may be formed in each of the dividedsections. At this point, the supermirror of the reflecting mirror 42should be changed according to the type of the supermirror of thereflecting mirror 40.

(4) Regarding the size, the curvature, or the like of the reflectingmirror 30 and the reflecting mirror 32 of the oblique incidence opticalsystem unit 12 and the reflecting mirror 40 and the reflecting mirror 42of the normal incidence optical system unit 14, or the size and theconstitution of the main unit 20 in the above-described embodiments,their dimensions may be set according to the observation objects of thereflecting mirrors (30, 32, 40, 42) and the space inside an observationsatellite in which the telescope is mounted.

It is to be noted that, when the broadband telescope according to ismounted in the observation satellite and the broadband telescope islocated on Lagrangian point (refer to L1 shown in FIG. 12) to observespace plasma around the earth, around the earth, for example, as shownin FIG. 12 and FIG. 13, various changes of specific dimension settingshould be performed.

In FIG. 13,

Oblique incidence telescope part (XRT part):

Mirror length of paraboloid of revolution (mirror length) L:200 mm;

Focal length (distance) F:600 mm;

Maximum incident angle a:15 degrees;

Mirror thickness t: 1.5 mm;

Outer diameter pr_(o):1020 mm;

Inner diameter: 200 mm;

Top coating: Pt (platinum) 50 nm,

Normal incidence telescope part:

Distance from focal point F (extended length) G:50 mm;

Primary mirror focal length f₁:200 mm;

Secondary mirror focal length f₂:−166.7 mm;

Composite focal length f:500 mm, and

Superconducting tunnel junction detector (STJ detector):

Detectable area size:11×11 mm² are set.

Furthermore, the number of the reflection mirrors 30 and the reflectionmirrors 32, which constitute the aspherical reflecting mirror 12 c ofthe oblique incidence optical system unit 12, may be smaller than thetotal number of the reflecting mirrors constituting the paraboloid andthe reflecting mirrors constituting the hyperboloid in the asphericalreflecting mirror of the oblique incidence telescope of so-called Woltertype I. In other words, the number of the reflection mirrors 30 and thereflection mirrors 32 is adjusted depending on the size and the positionof the normal incidence optical system unit 14, which is located in theinner diameter side of the aspherical reflecting mirror 12 c of theoblique incidence optical system unit 12, and the space inside the innerdiameter of the oblique incidence optical system unit 12 should bechanged.

Moreover, in the above-described embodiments, the approximatecolumnar-shaped aspherical reflecting mirror of so-called Wolter type I,which is used in the oblique incidence telescope, is disposed in theoblique incidence optical system unit 12, but it goes without sayingthat the invention is not limited to this. A different type ofreflecting mirror from the aspherical reflecting mirror of Wolter type Imay be disposed.

(5) In the above-described embodiment, when light extending form x-rayto visible region are detected simultaneously, there is a possibility ofallowing a light event on a low energy side to be cancelled into aphonon event produced by light having high energy due to thecharacteristics of the superconducting tunnel junction device 16.

For this reason, when band pass filters for severally selecting x-ray,soft x-ray, extreme ultraviolet ray, ultraviolet ray and visible lightray are disposed, spectral detection of light in the region extendingfrom x-ray to visible light can be performed more accurately.

At this point, a thin film filter utilizing absorptive structure ofmaterial, which is an Al/C (aluminum/carbon) metal thin film filter, forexample, can be used with respect to x-ray to vacuum ultraviolet ray(refer to FIG. 14(a), (b)), and a filer utilizing the absorptivestructure of material or a band pass filter utilizing interference canbe used with respect to vacuum ultraviolet ray to visible light ray.

Further, respective events of x-ray, soft x-ray, extreme ultravioletray, ultraviolet ray and visible light ray may be separated from thephonon event by the rise-up time of electrical signals, which isdetected as a result of incidence of reflected light to thesuperconducting tunnel junction device 16, without using such band passfilters.

This makes it possible to simultaneously detect light extending fromx-ray to visible region further accurately.

Furthermore, as the filter disposed in the prestage of thesuperconducting tunnel junction device 16, a filter for adjusting thequantity of light that is made incident to the superconducting tunneljunction device 16 may be used.

(6) In the above-described embodiment, a plurality of thesuperconducting tunnel junction devices 16 may be used to implementspectroscopic imaging, and in such a case, changes or the like ofvarious types of circuit systems may be made.

(7) The above-described embodiments and the modification examples shownin the above-described (1) to (6) may be combined appropriately.

Industrial Applicability

Since the present invention is constituted as described above, it exertssuperior effect that the advantages of the normal incidence opticalsystem and the oblique incidence optical system are utilized well andlight in a broad energy band, which is light in the region extendingfrom visible light to x-ray, for example, can be observed.

Further, since the present invention is constituted as described above,it exerts superior effect that a composite telescope of the normalincidence optical system and the oblique incidence optical systemreflects the light in a broad energy band that is the region extendingfrom visible light to x-ray, for example, at high reflectance, by whichcost reduction and space saving can be achieved and the light in a broadenergy band can be observed efficiently.

1. A broadband telescope, comprising: an oblique incidence opticalsystem unit where light is made incident obliquely to a surface partthat reflects incident light; a normal incidence optical system unitwhere light is made incident substantially vertically to a surface partthat reflects incident light; and a detector to which reflected lightreflected by the surface part of said oblique incidence optical systemunit and reflected light reflected by said surface part of the normalincidence optical system unit are made incident and which spectrallydetects the incident light.
 2. A broadband telescope as claimed in claim1, wherein said normal incidence optical system unit is located insidecomparing to said oblique incidence optical system unit, and saiddetector is located on an optical axis.
 3. A broadband telescope,comprising: an oblique incidence optical system unit, which has a firstreflecting mirror reflecting incident light at a first surface part madeup of paraboloid of revolution, and a second reflecting mirrorreflecting the light, which is reflected at said surface part of saidfirst mirror, at a second surface part made up of hyperboloid ofrevolution; a normal incidence optical system unit, which has a thirdreflecting mirror that has a third surface part on which a multilayerfilm is formed, which continuously changes periodic lengths along thedepth direction to reflect each light of a predetermined energy in aregion extending from vacuum ultraviolet ray to extreme ultraviolet rayand has high reflectance due to total reflection over a visible lightregion, and reflects the incident light at the third surface part, and afourth reflecting mirror that has a fourth surface part on which amultilayer film is formed, which continuously changes the periodiclengths along the depth direction corresponding to said third surfacepart of said third reflecting mirror to reflect each light of apredetermined energy in the region extending from vacuum ultraviolet rayto extreme ultraviolet ray and has high reflectance due to totalreflection over the visible light region, and reflects the light, whichis reflected at said third surface part of said third reflecting mirror,at the fourth surface part; and a detector to which reflected lightreflected at said second surface part of the second reflecting mirrorand light reflected at said fourth reflecting mirror are made incidentand which spectrally detects the incident light.
 4. A broadbandtelescope as claimed in claim 3, wherein said first reflecting mirrorand said second reflecting mirror of said oblique incidence opticalsystem unit constitute an aspherical reflecting mirror of an approximatecylindrical shape, said normal incidence optical system unit is locatedwithin the inner diameter side of the aspherical reflecting mirror, andsaid detector is located on an optical axis.
 5. A broadband telescope asclaimed in any one of claims 1, 2, 3 and 4, wherein said detector is asuperconducting tunnel junction device.
 6. A broadband telescope asclaimed in any one of claims 1, 2, 3, 4, said telescope furthercomprising: a filter that makes only light, which has higher energy thanthe reflected light reflected at the surface part of said normalincidence optical system unit out of the reflected light reflected atthe surface part of the oblique incidence optical system unit, incidentselectively to the detector.